DESCRIPTION (Investigator's Abstract): To perform skillful limb movements, we must be able to learn multiple motions in a specific temporal order. The cerebral substrates involved in acquiring temporally organized motor skills are not fully defined. The goal of this proposal is to localize changes of regional cerebral activity during normal motor learning of a sequential motor task. Brain mapping by imaging of cerebral blood flow using positron emission tomography (PET) will be use to identify the critical neural structures where these motor learning related changes occur. In humans, motor learning can occur with and without conscious involvement. Our broad hypothesis is that the brain is flexible in accessing different cerebral systems for motor learning, depending on behavioral modifiers as well as the temporal and kinematic complexity of a task. To test this, a highly reproducible motor learning paradigm will be used to systematically examine the functional contribution of cerebral areas implicated in motor learning. The paradigm is the serial reaction time task (SRT) in which the subjects learn specific motor sequences while pressing a keypad with their fingers. The task is kinematically simple, requiring only isolated finger movements. The learning paradigm is designed so that the effects of attention, awareness, cognitive strategy, and task complexity on motor learning can be determined. The following specific aims will be addressed. Differentiate perceptual and motoric components of motor sequence learning. Characterize the effect of attention on motor sequence learning. Identify the effect of awareness on motor sequence acquisition. On completion of these aims a comprehensive model of normal learning of temporally organized movements, based on both behavioral and functional imaging data, will be established. This biologically based learning model provides a powerful tool for determining how conscious strategies and behavioral conditions modify the localization of motor learning. This type of normal motor learning is one form of cerebral plasticity that can be used to understand adaption in response to disease. The results will be clinically relevant when the potential mechanisms underlying functional recovery after brain injury or degeneration are examined. Understanding the role of attention and awareness on motor learning will provide a first step in establishing a rational basis for the design of rehabilitation strategies directed at recovering motor function after focal brain injury.